Provide default implementations for NotificationDelegate methods.

chrome/browser/notifications/extension_welcome_notification_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/notifications/extension_welcome_notification.h"
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
@@ skipping 187 matching lines @@
   void SetInt64Pref(const char* path, int64 value) const {
     profile_->GetPrefs()->SetInt64(path, value);
   }
 
  private:
   class TestNotificationDelegate : public NotificationDelegate {
    public:
     explicit TestNotificationDelegate(const std::string& id) : id_(id) {}
 
     // Overridden from NotificationDelegate:
-    void Display() override {}
-    void Error() override {}
-    void Close(bool by_user) override {}
-    void Click() override {}
-    void ButtonClick(int index) override {}
-
     std::string id() const override { return id_; }
 
    private:
     ~TestNotificationDelegate() override {}
 
     const std::string id_;
 
     DISALLOW_COPY_AND_ASSIGN(TestNotificationDelegate);
   };
 
@@ skipping 309 matching lines @@
 
   EXPECT_TRUE(task_runner()->GetPendingTasks().empty());
   EXPECT_EQ(message_center()->add_notification_calls(), 0);
   EXPECT_EQ(message_center()->remove_notification_calls(), 0);
   EXPECT_EQ(message_center()->notifications_with_shown_as_popup(), 0);
   EXPECT_FALSE(GetBooleanPref(prefs::kWelcomeNotificationDismissed));
   EXPECT_TRUE(GetBooleanPref(prefs::kWelcomeNotificationDismissedLocal));
   EXPECT_TRUE(GetBooleanPref(prefs::kWelcomeNotificationPreviouslyPoppedUp));
   EXPECT_EQ(GetInt64Pref(prefs::kWelcomeNotificationExpirationTimestamp), 1);
 }